1. Field of the Invention
The present invention relates generally to spark plugs for internal combustion engines, and more specifically to spark plugs including firing ends having downward extending tines.
2. Related Art
A spark plug is the ignition source in an internal combustion engine. One end of the spark plug extends into a cylinder head of the internal combustion engine, thereby exposing two electrodes in the cylinder head, with a gap between the two electrodes. A compressed mixture of fuel vapor and air in the cylinder is ignited by establishing an electrical discharge across the gap between the two electrodes at predetermined time intervals. Since the spark plug is an integral part of the proper and efficient operation of the internal combustion engine, there have been many efforts to improve the performance of the spark plug.
The spark plug creates an electrical arc in the cylinder head to ignite the air-fuel mixture. It may take up to 40,000 volts (supplied by an ignition coil connected to the center electrode) to create an arc that is sufficient to jump from the center electrode to ground in the pressurized environment of the combustion chamber. As spark plugs wear, the edges of traditional center electrodes round off, thereby increasing the voltage required to jump the gap (and thus resulting in the need to replace spark plugs periodically). As the voltage required to jump the gap increases, the chance of misfire fouling and/or pre-ignition increases, thereby resulting in rough idling, poor performance, reduced gas mileage, and increased emissions.
Traditionally, the structure of the spark plug has included a concentric arrangement of the following components: (1) a cylindrical, high-voltage center electrode; (2) an insulator (e.g., a ceramic insulator) surrounding the center electrode; and (3) a threaded shell surrounding the insulator. The threaded shell is configured for screwing into a tapped hole providing access to the interior of the cylinder of the internal combustion engine. Typically, the shell includes a metallic appendage acting as the ground electrode. These traditional spark plugs may be referred to as ground-wire tip spark plugs. The metallic appendage is fused to the rim of the shell, in close proximity to the center electrode. The purpose of this structure is to protect the center electrode from the corrosive environment of the cylinder, while simultaneously enabling the rapid dissipation of heat from the end of the center electrode to the cylinder head and to the insulator. The center electrodes of spark plugs may be fabricated utilizing nickel-chrome steel hollow sheaths surrounding copper alloy center members, for example.
Some of the efforts in improving the traditional spark plug (e.g., improving the performance, durability, efficiency, etc.) have focused on the materials used to fabricate the spark plug. For example, stronger, more durable materials (e.g. platinum, gold palladium, copper-core fine wire, etc.) have been used to fabricate the center electrode, thus resulting in a somewhat longer lifespan of the spark plug. Other efforts have focused on the design of the firing end of the center electrode. For example, tapered tip and split-tip spark plugs have been developed, although at significantly higher cost.
There is an ongoing need for improved spark plugs that provide, inter alia, one or more of the following characteristics: greater heat exchange from the center electrode through the insulator; a greater number of potential pathways for the spark to proceed, such that the spark may follow the path of least resistance; better flow of electricity from the terminal through the electrode; and/or greater turbulence in the vicinity of the spark to move more of the air-fuel mixture into the space adjacent the spark. Each of these characteristics contributes to a hotter spark and longer life of the spark plug, and thus a more efficient combustion process. In addition to the foregoing, there is a need for spark plugs that: reduce emissions; eliminate the need for indexing; eliminate fouling; and/or eliminate the need to adjust ground wires (e.g., eliminate the need to adjust the spark plug gap).